proposal-system/api/src/ProposalSystem.Api/Middleware/InternalApiKeyMiddleware.cs

using System.Security.Claims;
using System.Security.Cryptography;
using System.Text;

namespace ProposalSystem.Api.Middleware;

public class InternalApiKeyMiddleware
{
    private readonly RequestDelegate _next;
    private readonly byte[] _apiKeyBytes;
    private readonly ILogger<InternalApiKeyMiddleware> _logger;

    public InternalApiKeyMiddleware(RequestDelegate next, IConfiguration configuration, ILogger<InternalApiKeyMiddleware> logger)
    {
        _next = next;
        _logger = logger;
        var key = configuration["INTERNAL_API_KEY"] ?? "";
        _apiKeyBytes = Encoding.UTF8.GetBytes(key);
    }

    public async Task InvokeAsync(HttpContext context)
    {
        if (_apiKeyBytes.Length > 0 &&
            context.Request.Headers.TryGetValue("X-Internal-Api-Key", out var providedKey) &&
            !string.IsNullOrEmpty(providedKey.ToString()))
        {
            var providedBytes = Encoding.UTF8.GetBytes(providedKey.ToString());
            if (CryptographicOperations.FixedTimeEquals(providedBytes, _apiKeyBytes))
            {
                var claims = new[]
                {
                    new Claim(ClaimTypes.NameIdentifier, "system"),
                    new Claim("sub", "system-lambda-caller"),
                    new Claim(ClaimTypes.Email, "system@proposal-system.internal"),
                    new Claim("email", "system@proposal-system.internal"),
                    new Claim("name", "System"),
                    new Claim(ClaimTypes.Role, "admins"),
                    new Claim("cognito:groups", "admins"),
                };
                var identity = new ClaimsIdentity(claims, "InternalApiKey");
                context.User = new ClaimsPrincipal(identity);
            }
            else
            {
                _logger.LogWarning("Invalid internal API key from {RemoteIp} on {Path}",
                    context.Connection.RemoteIpAddress, context.Request.Path);
            }
        }

        await _next(context);
    }
}